HTTP/1.1 Header Casing

When handling HTTP/1.1, Envoy will normalize the header keys to be all lowercase. While this is compliant with the HTTP/1.1 spec, in practice this can result in issues when migrating existing systems that might rely on specific header casing.

To support these use cases, Envoy allows configuring a formatting scheme for the headers, which will have Envoy transform the header keys during serialization. To configure this formatting on response headers, specify the format in the http_protocol_options. To configure this for upstream request headers, specify the formatting in http_protocol_options in the Cluster’s extension_protocol_options.

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